Medical research of nerve cells and research for the possibility of using nerve cells as electric devices are being made widely. When nerve cells become active, an action potential is generated. Ion density inside and outside of a nerve cell varies at first due to the alteration of the ion transparency, then the potential of the cell membrane alters. Therefore, it is useful to measure a two-dimensional distribution of the potential of the cell membrane for observing a sample cell or tissue. Measuring two-dimensional distribution of the potential provides a method for determining an active part and a level of the activity.
The inventors have developed an integrated combination electrode as the two-dimensional sensor that can be used for measuring cell membrane potentials of plural spots simultaneously without insertion of glass electrodes or other stimulating electrodes into the cell (Japanese Tokukaihei 6-78889, 6-296595). This integrated combination electrode includes many micro electrodes arranged in matrix and their lead pattern formed on a glass plate using conductive substances, on which a sample cell or tissue can be cultivated. This integrated combination electrode enables measuring potential alterations of plural spots in smaller pitch than glass electrodes or other conventional means. Furthermore, this integrated combination electrode enables long term observation of the sample cell or the tissue that are cultivated on the integrated combination electrode.
However, this integrated combination electrode is not suitable for an extensive use since it has a fixed size and a fixed pitch of measuring electrodes. In other words, it is difficult to use one integrated combination electrode for measuring different samples. In fact, different integrated combination electrodes were made by adjusting the size and pitch of electrodes to different samples.